Method for stretching and cutting sheet metal, and machine for carrying out the method



Jan. 6,- 1959 t F UNGERER 2,367,260 METHOD FOR STRETCHING AND CUTTING SHEET METAL, AND

MACHINE FOR CARRYING OUT THE METHOD Filed Jan. 11, 1954 INVENMIO FRry- UNGERER METHDD FGR STRETCHING AND CUTTING SHEET METAL, AND MACHINE F OR CARRY- ING OUT THE METHOD Fritz Ungerer, Pforzheim, Germany Application January 11, 1954, Serial No. 403,324 Claims priority, application Germany January 12, 1953 1 Claim. (Cl. 153-35) The present invention relates to a method for stretching and cutting sheet metal, and to a machine for carrying out the method.

It is a fact well known to the art that for the straightening of sheet metal of austenitic steel as well as for N. E.-sheet metal, straightening presses are not well suited, as the constant bending in one direction or the other, which the sheet metal undergoes during its passage between the straightening rollers, quickly results in cold deformation of the sheet metal and, consequently, in the loss of the original properties of the sheet metal. The result is that the yield point goes up, while the capacity of stretch goes down. Another drawback of straightening presses, when used for the straightening of austenitic sheet metal, is the fact that the sheet metal, after its passage between the rollers, is frequently provided on its surface with unsightly marks (stripes or the like) which make the sheet metal unsuited for use as an outer covering means.

On the other hand, for sheet metal of austenitic steel the straightening is particularly needed. Sheet metal of this kind is subjected in the annealing furnace to a heat treatment of 800 900 centigrade, and when leaving the furnace directly slides into a tempering bath, from which it emerges in highly undulating condition.

It is known to straighten sheet metal of this type by means of stretching machines. In a known machine of this kind, the sheet metal is seized at two oppositely disposed ends by grip heads, then straightened through stretching, and then removed from the grip heads. After this the cutting and further treatment of the sheet metal take place in customary manner. The decision about the point up to which the stretching is to go on, is left to the operator of the machine, so that it is necessary for the operator to constantly watch the surface of the sheet metal in order to make his decision.

According to the invention, the stretching of the sheet metal is considerably simplified and cheapened by the feature that the material, after having been seized by the grip heads in known manner and stretched to a predetermined stretching point indicated at a manometer scale, is, at lessening tension, cut off by shearing means provided at the grip heads, so that no special shearing step is required.

Furthermore, the stretching as disclosed in the present invention is effected preferably not at uniform speed throughout the entire stretching action, but at first quickly, until the tensioning of the sheet metal starts, and then :slowly, until the predetermined stretching point has been reached, whereupon the pull on the sheet metal again somewhat lessens until the tension in the sheet metal just about disappears. For the actuation of the grip heads hydraulic means should be used. But electromotive actuation is likewise possible.

For the correct timing of the various steps of the stretching, including the automatic actuation of the shearing means as well as the closing and opening of the grip heads, electric control means may be employed.

The machine is provided with a supporting table for the sheet metal of artificial material, from which the sheet metal can easily be withdrawn in lateral direction, and which prevents the sheet metal from dropping down and from becoming scratched. Prior to and after the stretching the sheet metal is piled up on stable supporting means suited for the purpose.

In order to adapt the machine to the working of sheet metal of varying length, it is necessary to devise the construction in such a way that rough adjustment of at least one of the 'grip heads is thereby enabled.

The machine is further provided, laterally of the grip heads, with suitable guiding means, consisting preferably of jawdike opening rows of rolls, permitting the easy feeding to the grip heads of even strongly undulating sheet metal. Guiding means of this kind may be provided on both sides of the grip heads.

It is further feasible to effect the hardening and annealing, if required, directly at the tensioned sheet metal by means of small travelling annealingand cooling zones. An arrangement of this kind prevents reliably the manufacture of large quantities of faulty metal sheets.

The invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawings, forming a part of this specification, and in which an embodiment of the invention has been shown by way of illustration. However, I wish to say that the invention is not confined to any strict conformity with the showing of the drawings, but may be changed or modified, so long as such changes or modifications mark no material departure from the salient features of the invention as expressed in the appended claim.

In the drawings, in which like parts are referred to by the same reference numerals in all of the several figures,

Fig. 1 is a side view of the stretching machine;

Fig. 2 is a top view of one of the grip heads;

Fig. 3 is a side view of a grip head, as per Fig. 2, on an enlarged scale.

Referring now to the drawings in detail, the reference numerals 2 and 3 denote the grip heads positioned at the ends of strong bolts 4 and 5. The bolt 3 is, by means of hydraulic pressure exerted in the block 7, displaced in the direction indicated by the arrow. Whereby the displacement proceeds at first quickly, until the sheet metal 10 gripped by the clamping jaws 8 and 9, has tensioned, and then slowly until a predetermined straightening or tensioning limit is indicated by a manometer (not shown in the drawings). The pull on the sheet metal 10 is then slightly lessened until the tension in the sheet metal just about disappears. After this the shearing blades 11 and 12 are actuated, either automatically or by the workman, with the result that the sheet metal drops down upon the table 13.

The sheet metal is pushed from the side via the jawlike opening rows of rolls 14 and 15 (see Fig. 3) into clamping positionbetween the clamping jaws 8 and 9 of the grip heads 2 and 3. The edge portions of the sheet metal which after the cutting remain between the clamping jaws, can easily be removed from the latter, or drop out by themselves.

The block 7 is stationarily mounted on the support 16.

The block 6 can be adjusted in steps via the notches 17 in working position, in conformity with the length of the sheet metal, through hydraulic pull exerted on the bolt 4 of grip head 2. It will be seen, therefore, that the stretching of the sheet metal is effected through displacement of the grip head 3, while the adjustment to the length of the sheet metal is eifected through displacement of the grip head 2.

What I claim as new and desire to secure by Letters Patent of the United States is:

Method of straightening wavy metal sheets comprising, in combination, the steps of clamping and thereby solely supporting a wavy metal sheet at two clamping lines located in aplane on opposite edge portions ofsaid sheet, applying a tensile force to said sheet along said clamping lines until the metal sheet is straightened and planar; pulling said opposite edge portions of the thusstraightened sheet until the straightened sheet ,is tensioned to a permanently straightened planar condition; reducing the pullling force on said opposite edge portions to substantiallyzero value; maintaining said sheet clamped at said twoclamping lines and simultaneously cutting the (fl, sheet in substantially un-tension ed condition adjacent both said edge portions inwardly of said clamping lines.

References Cited in the file of this patent UNITED STATES PATENTS 1,710,261 Kellogg Apr. 23, 1929 1,723,098 Ungerer Aug. 6, 1929 1,903,638 Sykes Apr. 11, 1933 2,003,094 Shimer May 28, 1935 2,336,524 Bannister Dec. 14, 1943' 2,442,268 Fields May 25, 1948 2,460,483 Berliner Feb. 1, 1949 2,493,560 Vasselli Ian. 3, 1950 FOREIGN PATENTS 9,137 Great Britain Apr. 18, 1906 588,186 Germany Nov. 14, 1933 

